Exploring new methods and materials for enantioselective separations and catalysis

Abstract

In this article, we will review and highlight some recent computational work on enantioselective adsorption and catalysis in zeolites and metal-organic frameworks. The design, development and understanding of chiral structures will help expand the utility of nanoporous materials into chiral technology. The highlighted works are examples of how molecular simulations can provide a fundamental understanding of chirality in nanoporous materials. This understanding is essential to help in the design and development of next-generation enantioselective separation devices and catalysts.

Comparison of the structure-directing effect of ephedrine and pseudoephedrine during crystallization of nanoporous aluminophosphates

“…Molecular structures of the organic molecules were described with the cvff forcefield [23]. Due to the strong basicity of ephedrine (pK a = 9.6) [24] the low pH of the synthesis medium (3)(4)(5), and the necessity for charge-balancing the negative charge imposed by the incorporation of dopants, protonated EPH and PsEPH molecules were studied. The atomic chargedistribution of the protonated cations was obtained from DFT+D calculations, using the B3LYP hybrid functional and the ESP charge calculation method, setting the total net charge to +1.…”

“…As a consequence, the metabolism of living beings differentiates between enantiomers of chiral compounds, very frequently having only one enantiomer the desired therapeutic effect [2]. In this context, the design of chiral solids able to discriminate between enantiomers of a chiral compound, either during separation or catalytic processes, represents one of the greatest challenges in contemporary chemical research [3,4]. In the quest for chiral functional solids, zeolites and crystalline nanoporous materials in general have been proposed as ideal candidates since they could potentially combine their high surface area and characteristic shapeselectivity with a potential enantioselectivity that might be enhanced by the confinement effect [5][6][7][8].…”

Supramolecular chemistry controlled by packing interactions during structure-direction of nanoporous materials: Effect of the addition of methyl groups on ephedrine derivatives

“…The way to induce enantio-differentiation is by subjecting the chiral compound to an asymmetric confined environment, where different enantiomers of the compound will interact differently with the environment. In this context, one of the greatest challenges nowadays is the development of homochiral solids able to discriminate between the enantiomers of chiral compounds [3,4]. Indeed, chiral surfaces (like those in d-or l-quartz) are in principle able to transfer their chirality to a particular separation/catalytic process and perform enantioselective operations [5].…”

Supramolecular chemistry of chiral (1R,2S)-ephedrine confined within the AFI framework as a function of the synthesis conditions

“…Homochirality is in contrast almost never found in inorganic systems (quartz exists in both enantiomorphic forms). However, there is evidence that chiral inorganic surfaces can transfer their chirality to adsorption or catalytic processes and perform enantioselectively [4], and hence the search of homochiral inorganic structures represents a fundamental area of research nowadays [5,6]. In this context, chiral zeolite-type microporous materials are optimum candidates for achieving such solids since they could combine their characteristic high adsorption capacity, stability and shapeselectivity with a potential enantioselectivity.…”